The donation was the largest charitable gift on public record in 2013, according to the Chronicle of Philanthropy, and marked the first time that donors under the age of 30 were responsible for the year's largest donation. Zuckerberg and Chan's 2013 donation was equal in shares to the gift the couple gave the same foundation in December 2012. That gift was valued at just under $500 million at the time, but the success of Facebook's stock over the past 12 months more than doubled the value of the 2013 donation.

The Siicon Valley Community Foundation serves as a gatekeeper to a number of different charitable causes. Donors provide the financial capital, and the foundation assists them in making sure their gift is presented to the appropriate charities. In 2013, the Silicon Valley Community Foundation awarded more than 10,000 grants to over 29 different countries, according to its website.

Of the top 15 public gifts in 2013, 12 were awarded to college or universities, including a $350 million pledge by Michael Bloomberg to Johns Hopkins University. In all, 15 different individuals (or couples) donated gifts of $100 million or more in 2013, an increase over 11 individuals in 2012, according to the Chronicle of Philanthropy.

Zuckerberg and Chan haven't stopped their charitable giving at 36 million shares. Zuckerberg signed the "Giving Pledge" in 2010, an agreement to give more than half of his wealth to charity over his lifetime or after his death. The "Giving Pledge" currently has more than 120 commitments, including Microsoft co-founder Bill Gates and wife Melinda, Berkshire Hathaway CEO Warren Buffett, and businessman Carl Icahn.

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